1. Field of the Invention
The present invention relates to, for example, a vehicle body frame of a motorcycle or the like, a die-cast product which constitutes a portion of the vehicle body frame, and a mold and a die-cast method for the die-cast product.
2. Description of Background Art
Among vehicle body frames of motorcycles, some vehicle body frames are manufactured by casting using light-weight metal such as aluminum. In manufacturing such vehicle body frames by casting, since it is necessary to make the inside of the vehicle body frame hollow to achieve the reduction of weight, casting is performed by setting a sand core in a mold. (See, for example, JP-A-1-254479.)
The core includes splints for setting the core in the mold and the core is set in the mold by inserting the splints into the mold. However, there exists a drawback that it is difficult to reflect the positional accuracy of the splints to the mold in which the splints are mounted. Particularly, even a slight distortion of the mold attributed to heat causes the interference of the splint with a splint mounting portion of the mold. Accordingly, to prevent the occurrence of damages on the splints at the time of clamping the mold, it is a prerequisite to ensure a large clearance between the splint mounting portion of the mold and the splint. As a result, when the core is displaced due to a molten flow at the time of casting, there arises a drawback that a wall thickness of a product becomes non-uniform.